1.Field of the Invention
This invention relates to a recording apparatus and more particularly to a recording apparatus called a serial type recording apparatus (or printer) which is arranged to perform recording by moving a carriage on which a recording head is mounted and by detecting the position of the carriage with a linear encoder,
2. Description of the Related Art
A magnetic encoder is a kind of linear encoder, The magnetic encoder consists of a linear magnetic scale part which is magnetized to alternately have opposite polarities in the longitudinal direction thereof at a predetermined pitch and a magnetic head which is arranged to be movable along the magnetic scale part and to detect the magnetic field of the magnetic scale part. The magnetic head is composed of a magnetoresistive element (hereinafter referred to as MR element). It has been proposed to arrange the serial type recording apparatus (or printer) to use this magnetic linear encoder in detecting the position of the carriage on which the recording head is mounted,
In the printer of the above-stated kind, the magnetic scale part is sometimes arranged to be used also as a guide shaft. In such a case, the magnetic scale part is formed in a cylindrical shape and used with a grease applied to it as a lubricant, The grease sometimes solidifies or has dust, ink, etc., stuck thereto. In such an instance, these substances tend to stick to the surface of the MR element and come to cause an electrical fault by corroding thin-film patterns which form the MR element.
Further, in a case where the magnetic linear encoder is to be used in a printer arranged to perform color recording in a high-density dot method, the magnetic scale part must be arranged in the following manner to meet requirements in respect to space saving, high speed responsivity, high precision, etc. The magnetic scale part is formed with a thin magnet wire made of an alloy of Fe-Cr-Co, Mn-Al-C or the like measuring about 1 mm in diameter. The magnetizing ranges of N and S poles formed on the wire are respectively set at an extremely small value not exceeding 50 .mu.m. Besides, with respect to durability, the MR element part of the magnetic head and the magnet wire must be kept apart from each other at the time of sliding. The space or gap between the MR element part and the magnetic wire thus must be held within 30 .mu.m or thereabout under these conditions. However, it is difficult to precisely set this gap because of the shape of the slider of the magnetic head. Therefore, the magnetic wire and the MR element part have sometimes come into contact with each other to bring about an electrical fault in the thin-film patterns.
This problem has heretofore been solved either by making the slider with a metal material to enhance the dimensional precision or by using an additional bearing. These solutions, however, have not been efficient as they either increase the number of parts or necessitate a much longer period of time in machining the parts.